The present invention relates to an axle shaft including an electromechanically or pneumatically actuated disc brake.
In known pressurized-air-actuated disc brakes, a braking operation is carried out by actuating the brake application device, for example, by way of a piston rod movement of a pneumatic brake cylinder. Via the piston rod, a connected brake lining is pressed against the brake disc. Depending on whether the disc brake is in the form of a fixed-caliper brake or a sliding- or pivoting-caliper brake (or as a combination of these types of brakes), either the brake disc is moved, in particular pushed, against the further brake lining on the other side of the brake disc and/or the further brake lining is moved, in particular pushed, against the brake disc.
One disadvantage is that a torque is produced about an axis of the disc brake during braking operations, and this leads to skewing of the brake caliper in relation to the brake disc.
An object of the invention is, therefore, initially to avoid this disadvantageous effect in a manner which is simple in terms of design.
This, and other, objects are achieved by providing an axle shaft including an electromechanically or pneumatically actuated disc brake, in particular for a commercial vehicle. The disc brake includes a brake caliper and a brake disc, the caliper surrounding at least portions of the outer circumference of the brake disc in a frame-like manner. A brake application device performs a brake application movement, and at least one adjusting device, preferably a plurality of adjusting devices, adjusts the air play between the brake pads and the brake disc on each side of the brake disc. The brake disc and the brake caliper move in relation to one another, and the brake caliper on the axle shaft is fixed to at least two fixing lugs, which preferably extend away from the axle shaft in different directions at at least one or more fixing points in each case. The fixing lugs and the fixing points of the brake caliper (or of an optional brake carrier formed on the fixing lugs) are oriented and/or formed such that there is either no displacement of the fixing points on the fixing lugs perpendicular to the brake disc or there is an identical parallel displacement of the fixing points on both fixing lugs perpendicular to the brake disc.
Advantageous refinements of the invention are described and claimed herein.
The present invention produces an arrangement and/or design of the fixing lugs and the fixing points of the brake caliper, or of an optional brake carrier, on the wheel lugs such that, during braking operations, there is either no displacement of the fixing points perpendicular to the brake disc on the fixing lugs or there is an identical parallel displacement of the fixing points perpendicular to the brake disc on both fixing lugs.
To this end, at least one, or both, of the fixing lugs is/are preferably oriented at the same angle or preferably at different angles to the brake disc or to the plane of the brake disc.
In this way, the invention initially eliminates the effect of the brake caliper becoming skewed during braking operations in a markedly simple and virtually cost-neutral manner, and independently of whether the caliper is in the form of a fixed caliper, a sliding caliper, or a pivoting caliper.
In the case of sliding—and pivoting-caliper designs, the invention prevents additional movement of the brake caliper, which results from the rotation of the fixing lugs (also see the detailed explanations of FIGS. 2 and 3, as well as 4).
However, the invention is furthermore also surprisingly suitable, given appropriate configuration, for producing a brake caliper which is preferably formed without sliding or rotary bearings, but which nevertheless is arranged on the axle shaft such that it can move in such a way that a displaceable brake disc can be dispensed with when a fixed-caliper design is used if adjusting devices are arranged on both sides of the brake disc. This omission of bearing elements both on the brake caliper and on the brake disc leads to a further considerable reduction in production costs.
This will be explained in greater detail in the text which follows.
In the case of fixed-caliper brakes with a brake application or actuating apparatus only on one side of the brake disc and adjusting devices on both sides of the brake disc, see, for example, WO 02/14708, a brake lining on the brake application side is first pressed against a brake disc and then the brake disc, which can preferably move in the axial direction but is mounted on a wheel hub or another component such that it transmits torque, is pressed against the further brake lining, which is preferably stationary in relation to the fixed caliper, as a result of axial displacement and so as to overcome air play. A feasible alternative/option is to form the fixed caliper such that it can perform micromovements itself in such a way that, during braking operations, it moves alone or in interaction with a moving brake disc such that the reaction forces are compensated for, or in such a way that there is sufficient relative movement between the fixed caliper and the brake disc to press the brake disc against the reaction-side brake lining too.
The relative movement between the brake disc and the caliper can be performed by an elastic movement, in particular pivoting, of the brake caliper on its fixture on the axle shaft of the wheel axle of the vehicle if the brake caliper is fixed to the axle shaft using lugs (or projections such as struts or the like), which move somewhat elastically under the action of the brake application forces.
One disadvantage of this solution is that a relatively high actuating force needs to be exerted on the brake disc on one side in order to move the brake caliper on the axle shaft, as a result of which the brake disc is loaded with axial forces, which often result in uneven loading and thus uneven wear of the brake linings on the brake application side and the reaction side of the brake disc.
In order to keep this uneven loading low, it is feasible to keep the brake fixing lugs very stiff in the circumferential direction, but to form them to be very resilient in the required movement direction parallel to the vehicle axle.
However, this is possible only to a relatively limited degree since the brake is also subjected to high lateral acceleration time and again during driving operation, and this can also lead to severe lateral vibration of the brake caliper in the case of an unstable fixing.
In contrast, an embodiment of the invention with a movable brake caliper on the axle shaft is fixed in a stable manner (in terms of fixing on the vehicle part) in such a way that impermissible lateral vibrations are prevented and wear on the brake disc and brake linings is as uniform as possible on the reaction side and the brake application side.
By suitably arranging the fixing points on the fixing lugs (by way of one or more fixing points or locations in each case), the tangential force acting on the fixing elements produces deliberate instances of deformation, which move the brake caliper toward the brake disc against the deformation resistance of the fixing elements on the reaction side of the brake disc.
Depending on the arrangement, the axial force which comes into effect is selected to be so great that the deformation resistances are overcome and also so great that the outer brake lining is actively pressed in the sense of self-reinforcement of the disc brake.